You mean they have outlawed bamboo/river cane, hickory splints, and thistledown?
Bamboo makes a nice little blowgun- the root end of a small cane makes a good reamer to knock the chamber walls out of the large blowgun cane, and if you have a bit of tin can lid you can perforate it and use it to tip the reamer and make it even better. The cane can be cut to whatever length is suitable by using a chert flake or knife to cut a groove around the cane and the cane will neatly snap at that point. A little heat straightens cane if it is needed. Use the big end as the mouthpiece and the natural taper of the cane compresses the air and improves velocity.
As for poison, I reckon any old stinking pile of crap will do...or maybe cane toad or castor bean toxin, both rather common around here and accessible, if there isn't anything in more commercial lying around. Poison isn't worth the bother for small game.